Terrorist explosive devices have produced the largest portion of terrorist casualties among civilian and military personnel compared to all other terrorist tactics. Commonly, the weapons used in such terrorist attacks are exploding vests and remotely detonated anti-personnel devices.
Numerous types of apparatus and methods have been utilized to detect and characterize such explosive devices, for example millimeter wave imaging, passive terahertz imaging, infrared imaging, trace chemical detection.
One such approach is imaging. But imaging techniques, by their nature, incur significant costs in exposure time and distance to produce information that is minimally relevant and not easily interpreted. Passive imaging systems are further challenged by low flux and high background.
Another approach is “sniff and wipe” technology. This technique relies on traces of specific explosives in air or on surfaces. However, bombers are using those same commercial sniffers and gateways to help them test their devices to evade trace detection.
Specific prior art technology includes:
1. Passive Imaging of Millimeter Wave Radiation.
Humans are said to be natural emitters of millimeter wave radiation. Camera-like systems for imaging millimeter wave radiations are reportedly under development or being offered by Millitech Corp. (Millivision), of South Deerfield, Mass. Detection of weapons and explosives and other concealed objects is said to be enabled by the differences in the amount of millimeter wave emission by those objects and humans and clothing. The drawbacks of this approach include that the images need to be interpreted by human operators or software. Also, exposure times are reported to be long.
2. Ultrasound for Remote Imaging of Concealed Weapons.
ATAG-Titan has developed a breadboard model of a system that is said to be able to detect metal and other hard objects under clothing at a distance of 8 m, and that can image objects at a distance of 5 m. However, operators need to be trained to interpret the images which are vague in appearance. Also, the 5 m distance is inadequate for safe explosives detection.
3. Chemical Trace Detection.
Several devices are marketed that detect trace chemicals from explosives or drugs. Most such devices are portal type or require mechanical contact with the subject and so are not directly related to this application. Variants are being developed that stimulate radiation from trace chemicals and so could be used at some distance. It seems likely that when such devices are deployed, the bomb makers will learn to remove trace chemicals from the exteriors of their devices.
4. IR Imaging.
IR imaging using IR pass filters in ambient light is also known art. Drawbacks of this approach include exposure times are long and/or the method can only to “see” through trivial thickness of clothing and/or at close range.
The prior art devices have significant shortcomings including long exposure times, low or non sensitivity to non-metallic materials, limited distances of operation. Trace chemical detection devices have further shortcomings in that explosive devices can be prepared in such a ways as to avoid trace detection.